Steering control device and steering control method

Abstract

A steering control device (10) executes an operation amount calculation process, an estimation process, a correction process, and an operation process. The operation amount calculation process is a process for calculating an operation amount for control using a steering torque as a control amount and using a target steering torque as a target value for the control amount. The estimation process is a process for estimating a disturbance torque using a nominal model and a filter. The correction process is a process for correcting the operation amount on the basis of the disturbance torque estimated by the estimation process. The operation process is a process for operating a motor of the steering device so as to generate a torque corresponding to the operation amount corrected by the correction process. The number of polynomials of the denominator of the transfer function of the filter is greater than the number of polynomials of the denominator of the transfer function of the nominal model.

Description

Technical Field

[0001] The invention relates to a steering control device and a steering control method. Background Art

[0002] For example, the following Patent Document 1 describes a device for operating a motor for steering a steering wheel according to an operation amount of feedback control using a steering torque as a control amount and a target value of the steering torque as a target value of the control amount. Specifically, the operation amount of feedback control is calculated based on an output value of a proportional component, an output value of a differential component, and an output value of an integral component.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2004-203089

[0004] However, when feedback gain is set to meet the requirement of improving the responsiveness of the feedback control, the time required to adjust the value of the feedback control parameter to meet the requirement may become too long. Summary of the invention

[0005] In one embodiment of the present invention, a steering control device is provided. The steering control device is configured to perform operation amount calculation processing, inference processing, correction processing, and operation processing, wherein the operation amount calculation processing is processing for calculating the operation amount of control using a steering torque as a control amount and using a target steering torque as a target value of the control amount, the steering torque is a torque input to a steering device by a driver, and the target steering torque is a target value of the steering torque, the inference processing is processing for inferring a disturbance torque using a nominal model and a filter, the correction processing is processing for correcting the operation amount based on the disturbance torque inferred by the inference processing, the operation processing is processing for operating the motor of the steering device in a manner of generating a torque corresponding to the operation amount corrected by the correction processing, and the degree of the polynomial of the denominator of the transfer function of the filter is greater than the degree of the polynomial of the denominator of the transfer function of the nominal model.

[0006] In another embodiment of the present invention, a steering control method is provided. The steering control method includes: executing operation amount calculation processing, inference processing, correction processing, and operation processing, the operation amount calculation processing is a processing of calculating the operation amount of control using a steering torque as a control amount and using a target steering torque as a target value of the control amount, the steering torque is a torque input to a steering device by a driver, the target steering torque is a target value of the steering torque, the inference processing is a processing of inferring a disturbance torque using a nominal model and a filter, the correction processing is a processing of correcting the operation amount based on the disturbance torque inferred by the inference processing, the operation processing is a processing of operating the motor of the steering device in a manner of generating a torque corresponding to the operation amount corrected by the correction processing, and the degree of the polynomial of the denominator of the transfer function of the filter is greater than the degree of the polynomial of the denominator of the transfer function of the nominal model. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a diagram showing the configuration of a steering control device and a steering device according to the first embodiment.

[0008] Figure 2 Yes means Figure 1 A block diagram of the processing performed by a steering control device.

[0009] Figure 3 Yes means Figure 2 Graph showing characteristics of the filter in and characteristics of the filter of the comparative example.

[0010] Figure 4 This is a block diagram showing processing executed by the steering control device according to the second embodiment.

[0011] Figure 5 It is a diagram showing the configuration of a steering control device and a steering device according to a third embodiment.

[0012] Figure 6 Yes means Figure 5 A block diagram of the processing performed by a steering control device. DETAILED DESCRIPTION

[0013] <First Embodiment>

[0014] Hereinafter, a first embodiment will be described with reference to the drawings.

[0015] "Premise Structure"

[0016] like Figure 1As shown in FIG. 1 , the steering device 10 includes a steering wheel 12. The steering wheel 12 is a mechanism for transmitting the driver's steering operation. The steering wheel 12 is connected to a transmission shaft 14. Therefore, if the steering wheel 12 rotates, the transmission shaft 14 rotates integrally. The rotational power of the transmission shaft 14 is transmitted to the steering shaft 16. The steering shaft 16 is arranged along the vehicle width direction ( Figure 1 The steering shaft 16 extends in the left-right direction. Steering wheels 20 are connected to both ends of the steering shaft 16 via steering tie rods 18.

[0017] The transmission shaft 14 is arranged to intersect with the steering shaft 16. Teeth that mesh with each other are formed on the transmission shaft 14 and the steering shaft 16. Moreover, by meshing the teeth with each other, power can be transmitted from the transmission shaft 14 to the steering shaft 16. That is, the rotational power of the transmission shaft 14 is converted into axial displacement power of the steering shaft 16. The axial displacement of the steering shaft 16 is transmitted to the steering wheel 20 via the steering tie rod 18. As a result, the steering angle of the steering wheel 20 is changed. In addition, the steering angle is the rotation angle of the tire.

[0018] In addition, the steering device 10 includes an auxiliary motor 30. The auxiliary motor 30 generates a force for assisting the driver's steering operation, that is, an auxiliary force. The rotational power of the auxiliary motor 30 is applied to the drive shaft 34. Teeth that are meshed with each other are formed on the drive shaft 34 and the steering shaft 16. Moreover, by the meshing of the above-mentioned teeth with each other, the power can be transmitted from the drive shaft 34 to the steering shaft 16. That is, the rotational power of the drive shaft 34 is converted into the axial displacement power of the steering shaft 16. Thus, the rotational power of the auxiliary motor 30 is converted into the axial displacement power of the steering shaft 16 via the drive shaft 34. In detail, the auxiliary motor 30 is, as an example, a three-phase brushless motor. In addition, the output voltage of the inverter 32 is applied to the terminals of the auxiliary motor 30.

[0019] The steering control device 40 controls the control amount of the steering device 10 as a control object. In order to control the control amount, the steering control device 40 refers to the steering torque Th input to the steering wheel 12. The steering torque Th is detected by the torque sensor 50. The torque sensor 50 is a sensor that detects the steering torque Th based on the degree of torsion of the torsion bar 52, which is a part of the transmission shaft 14. In addition, the steering control device 40 refers to the vehicle speed SPD detected by the vehicle speed sensor 54. In addition, the steering control device 40 refers to the rotation angle θa of the assist motor 30 detected by the rotation angle sensor 56. In addition, the steering control device 40 refers to the currents iu, iv, and iw flowing in the assist motor 30.

[0020] The steering control device 40 includes a PU 42 and a storage device 44. The PU 42 is a software processing device such as a CPU, a GPU, and a TPU. The storage device 44 includes a storage medium such as an electrically erasable non-volatile memory and a magnetic disk medium. A steering control program 44a is stored in the storage device 44. The steering control device 40 controls the control amount by executing the steering control program 44a stored in the storage device 44 through the PU 42.

[0021] “Processing performed by the steering control device 40”

[0022] exist Figure 2 2 shows the processing executed by the steering control device 40. Figure 2 The processing shown is realized by the PU 42 executing the steering control program 44 a at a predetermined cycle, for example.

[0023] The target steering torque calculation process M10 is a process for calculating the target value of the steering torque Th, that is, the target steering torque Th*, based on the axial force Fa. The axial force Fa is a force applied to the steering shaft 16. However, the axial force Fa is converted into the torque of the transmission shaft 14. In addition, the target steering torque calculation process M10 includes a process for setting the target steering torque Th* to different values ​​according to the vehicle speed SPD even if the axial force Fa is the same. This is a setting intended to allow the driver to feel the optimal steering feel corresponding to the vehicle speed SPD.

[0024] The open-loop operation amount calculation processing M12 is a processing for calculating the open-loop operation amount Mff. The open-loop operation amount Mff is the operation amount of open-loop control using the steering torque Th as the control amount and the target steering torque Th* as the target value of the control amount. The open-loop operation amount calculation processing M12 is a processing for calculating the open-loop operation amount Mff by inputting the target steering torque Th*. The open-loop operation amount calculation processing M12 calculates the open-loop operation amount Mff based on the inverse model of the nominal model Pn. The nominal model Pn is a model that uses the torque of the assist motor 30, that is, the assist torque Ta, as an input and outputs the estimated value of the steering torque Th, that is, the estimated steering torque The. Here, the assist torque Ta is a value converted into the torque of the transmission shaft 14. The inverse model is a model that uses the estimated steering torque The as an input and outputs the assist torque Ta. In addition, the nominal model Pn will be described in detail later.

[0025] The deviation calculation process M14 is a process for calculating a deviation which is a value obtained by subtracting the target steering torque Th* from the steering torque Th.

[0026] The feedback operation amount calculation processing M16 is a processing for calculating the feedback operation amount Mfb using the deviation as an input. The feedback operation amount Mfb is the operation amount of feedback control using the steering torque Th as the control amount and the target steering torque Th* as the target value of the control amount. The feedback operation amount Mfb is the sum of the output value of the proportional component using the deviation as an input and the output value of the differential component using the deviation as an input. In addition, the feedback operation amount Mfb is a value converted into the torque of the transmission shaft 14. In detail, the feedback operation amount calculation processing M16 includes a processing for changing at least one of the gain of the proportional component and the gain of the differential component according to the vehicle speed SPD.

[0027] The torque command value calculation processing M20 is a processing for calculating the auxiliary torque Ta using the open-loop operation amount Mff, the feedback operation amount Mfb and the estimated second disturbance torque de as inputs. In the torque command value calculation processing M20, the value obtained by subtracting the estimated second disturbance torque de from the sum of the open-loop operation amount Mff and the feedback operation amount Mfb is substituted into the auxiliary torque Ta.

[0028] The assist torque Ta is input to the axial force calculation process M22. The axial force calculation process M22 is a process of substituting the sum of the assist torque Ta and the steering torque Th into the axial force Fa.

[0029] The assist torque Ta is input to the disturbance observer M30. The disturbance observer M30 includes a steering torque estimation process M32, a first disturbance calculation process M34, and a second disturbance calculation process M36.

[0030] The steering torque estimation process M32 is a process for outputting an estimated steering torque The by inputting the assist torque Ta to the nominal model Pn. The estimated steering torque The is a steering torque assumed by the nominal model Pn.

[0031] The first interference calculation processing M34 is a processing for calculating and inferring the first interference torque dhe. The inferred first interference torque dhe is the interference component in the steering torque Th of the actual control object. The inferred first interference torque dhe is the difference between the actual torque and the torque inferred from the nominal model Pn. In other words, the inferred first interference torque dhe is the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. In detail, the first interference calculation processing M34 is a processing for substituting the value obtained by subtracting the inferred steering torque The from the steering torque Th into the inferred first interference torque dhe.

[0032] The second disturbance calculation process M36 is a process for calculating the estimated second disturbance torque de by taking the estimated first disturbance torque dhe as an input. The estimated second disturbance torque de is a disturbance torque converted into the torque of the assist motor 30. The second disturbance calculation process M36 is a process for calculating the estimated second disturbance torque de using the inverse model of the nominal model Pn and the filter Hd.

[0033] The filter Hd is provided to reduce noise caused by the differential operation included in the nominal model Pn. In the present embodiment, the filter Hd is, as an example, a third-order low-pass filter.

[0034] As described above, the assist torque Ta is a value obtained by subtracting the estimated second disturbance torque de from the sum of the open-loop operation amount Mff and the feedback operation amount Mfb. On the other hand, the estimated second disturbance torque de is a value obtained by converting the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th into the torque of the assist motor 30. This means that the estimated second disturbance torque de is a value corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. Therefore, the assist torque Ta is a value obtained by correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb according to the correction amount corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0035] The operation signal generation process M40 is a process for operating the inverter 32 by inputting the assist torque Ta. Specifically, the operation signal generation process M40 is a process for calculating the operation amount using the torque of the assist motor 30 as the control amount and using the target value of the assist torque Ta as the control amount converted into the torque of the assist motor 30. In addition, the operation signal generation process M40 includes a process for operating the inverter 32 in a manner to obtain the same operation amount. The operation amount may be, for example, the ratio of the off operation time of the switching element of the inverter 32 to one cycle of its on / off operation. Figure 2 , an operation signal MS for the inverter 32 is described. However, in reality, the operation signal MS is an individual operation signal for each switching element of the inverter 32.

[0036] "Nominal Model Pn"

[0037] The steering torque Th is expressed by the following formula (c1) using the inertia coefficient Jh, the viscosity coefficient Ch, and the steering angle θh. In addition, the inertia coefficient Jh represents the inertia of the first portion of the transmission shaft 14, which is closer to the steering wheel 12 than the torsion bar 52. In addition, the viscosity coefficient Ch represents the viscosity of the first portion of the transmission shaft 14. In addition, the steering angle θh is the rotation angle of the steering wheel 12.

[0038] -Th=(Jh·s·s+Ch·s)·θh…(c1)

[0039] On the other hand, when the rotation angle θ1 and the torsional rigidity coefficient Ktb of the torsion bar 52 are used, the following equation (c2) holds true. The rotation angle θ1 is the rotation angle of the second portion of the transmission shaft 14 that is farther from the steering wheel 12 than the torsion bar 52 .

[0040] Th=Ktb·(θh-θl)…(c2)

[0041] In addition, when the inertia coefficient J, the viscosity coefficient C and the elastic coefficient K are used, the following formula (c3) holds true between the rotation angle θl, the auxiliary torque Ta and the steering torque Th. The inertia coefficient J represents the inertia of the second part of the transmission shaft 14. In addition, the viscosity coefficient C represents the viscosity of the second part of the transmission shaft 14. In addition, the elastic coefficient K represents the elasticity of the second part of the transmission shaft 14. In addition, the viscosity coefficient C and the elastic coefficient K actually reflect the influence of the steering shaft 16, the steering tie rod 18 and the steering wheel 20 on the transmission shaft 14.

[0042] Th+Ta=(J·s·s+C·s+K)·θl...(c3)

[0043] Here, if the steering torque Th is inputted so that the steering angle θh becomes zero, the steering angle θh is always zero. When the transfer function from the assist torque Ta to the steering torque Th is calculated based on the above equations (c1) to (c3) with the steering angle θh set to zero, the following equation (c4) can be obtained.

[0044] Th / Ta=(-Ktb) / {J·s·s+C·s+K+Ktb}…(c4)

[0045] In the above formula (c4), the differential operator s is used. The above formula (c4) is a nominal model Pn. In addition, the above formula (c4) is valid even if "θh" and "θl" are read as follows in the above formulas (c1) to (c3).

[0046] θh: Phase difference of the rotation angle of the first portion of the transmission shaft 14 relative to the rotation angle of the steering wheel 12. It is always zero.

[0047] θl: a phase difference between the rotation angle of the second portion of the transmission shaft 14 and the rotation angle of the steering wheel 12 .

[0048] Therefore, the above-mentioned equation (c4) holds true for any steering angle θh.

[0049] "About Filter Hd"

[0050] In the present embodiment, in the transfer function of the filter, the degree of the denominator polynomial is 3, and the degree of the numerator polynomial is 0. In detail, the transfer function of the filter is the cube of "ω / (s+ω)". Here, the cutoff frequency ω and the differential operator s are used for the transfer function of the filter. In addition, the degree of the polynomial is the highest degree of the differential operator. In addition, hereinafter, a monomial is regarded as a polynomial in which all values ​​except one term are zero.

[0051] The above setting of the transfer function of the filter is a setting intended to effectively attenuate high-frequency noise.

[0052] That is, the purpose of the filter Hd is to suppress the high-frequency noise generated by the differential component contained in the inverse model of the nominal model Pn. Here, the polynomial of the denominator of the transfer function of the nominal model Pn is quadratic, so as long as the polynomial of the denominator of the transfer function of the filter Hd is set to quadratic, the influence caused by the differential component can be suppressed.

[0053] However, if Figure 3 As shown, compared with the second-order filter, the third-order filter can further attenuate the signal in the high-frequency region than the cutoff frequency ω. Therefore, in this embodiment, a third-order filter is used. In addition, Figure 3 The transfer function of the second-order filter of the comparative example in is the square of "ω / (s+ω)".

[0054] <Functions and Effects of the Present Embodiment>

[0055] PU42 uses the difference between the steering torque Th and the estimated steering torque The, that is, the estimated first disturbance torque dhe, as an input to calculate the estimated second disturbance torque de. The estimated second disturbance torque de represents the disturbance component of the torque of the second part of the transmission shaft 14. In other words, it represents the disturbance component in the torque converted into the force that displaces the steering shaft 16.

[0056] PU42 uses the value obtained by correcting the open-loop operation amount Mff and the feedback operation amount Mfb by the estimated second disturbance torque de as the assist torque Ta. Moreover, PU42 operates the inverter 32 in such a way that the torque of the assist motor 30 is close to the assist torque Ta. As a result, it is possible to perform control that compensates for the error between the nominal model Pn and the actual control object, that is, the disturbance component, and uses the target steering torque Th* as the target value of the control amount. In other words, it is possible to perform control that compensates for the error of the nominal model Pn relative to the actual control object and uses the target steering torque Th* as the target value of the control amount through the disturbance observer M30.

[0057] In this way, the error equivalent value is immediately compensated, so that the responsiveness of the steering torque Th with respect to the target steering torque Th* can be improved.

[0058] In addition, compared with the case where the controller is designed according to the actual control target without using the disturbance observer M30, the man-hours required for designing the controller can be reduced.

[0059] Furthermore, the second interference calculation process M36 is set as a synthesis process of the inverse model of the nominal model Pn and the filter Hd. Furthermore, the polynomial of the denominator of the transfer function of the filter Hd is set to be cubic. Thus, compared with the case where the polynomial of the denominator of the transfer function of the filter Hd is set to be quadratic, the attenuation effect of high-frequency noise can be improved.

[0060] According to the present embodiment described above, the following operations and effects are also achieved.

[0061] In (1-1) Figure 2 In the process shown, when the actual control object is set to the actual device P, the transfer function from the assist torque Ta to the steering torque Th is as follows.

[0062] 1 / {(1-Hd) / P+Hd / Pn}

[0063] Here, in the low frequency region lower than the cutoff frequency ω, as Figure 3 As shown, the gain of the filter Hd is close to “1.” Therefore, the transfer function from the assist torque Ta to the steering torque Th approximates the nominal model Pn itself.

[0064] On the other hand, PU42 calculates the open-loop operation amount Mff by inputting the target steering torque Th* to the inverse model of the nominal model Pn. Therefore, the transfer function from the target steering torque Th* to the steering torque Th is approximately "1". In other words, the transfer function of the output steering torque Th, which uses the input of the open-loop operation amount calculation processing M12 as an input and includes the disturbance observer M30 and the actual device P, is approximately "1". Therefore, it is possible to linearize the target steering torque Th* as an input to the steering torque Th as an output.

[0065] (1-2) The assist torque Ta includes the feedback operation amount Mfb. Thus, the error equivalent value of the designated second disturbance torque de can be compensated by the feedback operation amount Mfb. Therefore, the steering torque Th can be approximated to the target steering torque Th* with higher accuracy.

[0066] (1-3) The nominal model Pn is configured by including not only the inertia coefficient J but also the viscosity coefficient C, the elastic coefficient K, and the torsional rigidity coefficient Ktb. Thus, the nominal model Pn can be set as a model that approximates the actual control object with high accuracy.

[0067] <Second Embodiment>

[0068] Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

[0069] In this embodiment, the nominal model Pn is simplified.

[0070] exist Figure 4 The processing performed by the steering control device 40 of this embodiment is shown in FIG. Figure 4 In the process shown, for convenience, Figure 2 The same reference numerals are used to denote corresponding processes shown in the drawings.

[0071] like Figure 4 As shown in the steering torque estimation processing M32a, in the present embodiment, the nominal model Pn is represented by the following formula (c5).

[0072] (-Ktb) / {J·s·s}…(c5)

[0073] That is, the nominal model Pn does not have the terms of the viscosity coefficient C and the elastic coefficient K. Here, the viscosity coefficient C and the elastic coefficient K need to be estimated and determined according to the actual vehicle. In contrast, the inertia coefficient J is roughly determined by the inertia of the auxiliary motor 30 and the ratio of the rotation speed of the transmission shaft 14 in the steering device 10 to the rotation speed of the auxiliary motor 30, that is, the attenuation ratio. In addition, the torsional rigidity coefficient Ktb is determined by the characteristics of the torsion bar 52 of the torque sensor 50. Therefore, by omitting the terms of the viscosity coefficient C and the elastic coefficient K from the nominal model Pn, the man-hours spent on the design of the nominal model Pn can be reduced.

[0074] <Third Embodiment>

[0075] Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

[0076] "Premise Structure"

[0077] exist Figure 5 The structure of the steering control system of this embodiment is shown in FIG. Figure 5 For convenience, Figure 1 Corresponding parts are provided with the same reference numerals.

[0078] like Figure 5 As shown, in the steering device 10, the transmission shaft 14 is separated into an input shaft 14a connected to the steering wheel 12 and an output shaft 14b engaged with the steering shaft 16. In addition, in this embodiment, the output shaft 14b is actually not required. However, the output shaft 14b is provided for the convenience of the following description.

[0079] The input shaft 14a is provided with a reaction force motor 70. The reaction force motor 70 is a motor for applying a torque in a direction opposite to the torque input by the driver, that is, a reaction force, to the steering wheel 12. As an example, the reaction force motor 70 is a three-phase brushless motor. In addition, the output voltage of the inverter 72 is applied to the terminals of the reaction force motor 70.

[0080] The torque of the steering motor 80 is applied to the steering shaft 16 via the drive shaft 34. As an example, the steering motor 80 is a three-phase brushless motor. In addition, the output voltage of the inverter 82 is applied to the terminal of the steering motor 80.

[0081] The steering control device 40 controls the steering device 10. The steering control device 40 operates the inverter 72 to control the reaction force, which is the control amount of the control object. The steering control device 40 also operates the inverter 82 to control the steering angle of the steering wheel 20, which is the control amount of the control object.

[0082] The steering control device 40 refers to the rotation angle θs of the reaction force motor 70 detected by the rotation angle sensor 90 in order to control the reaction force, which is the control amount. In addition, the steering control device 40 refers to the currents ius, ivs, and iws flowing to the reaction force motor 70 in order to control the reaction force. In addition, the steering control device 40 refers to the rotation angle θt of the steering motor 80 detected by the rotation angle sensor 92 in order to control the steering angle, which is the control amount. In addition, the steering control device 40 refers to the currents iut, ivt, and iwt flowing in the steering motor 80 in order to control the steering angle.

[0083] “Processing performed by the steering control device 40”

[0084] exist Figure 6 The processing performed by the steering control device 40 is shown in FIG. Figure 6 FIG. 2 shows the processing performed by the steering control device 40 when the power transmission from the steering wheel 12 to the steering wheel 20 is cut off. Figure 6 For convenience, Figure 2 The same reference numerals are used to denote corresponding processes shown in the drawings.

[0085] like Figure 6As shown, the deviation calculation process M14 is a process for calculating a value obtained by subtracting the steering torque Th from the target steering torque Th*. The torque command value calculation process M20 is a process for outputting the reaction force command value Tr*. The torque command value calculation process M20 is a process for substituting a value obtained by subtracting the estimated second disturbance torque de from the sum of the open loop operation amount Mff and the feedback operation amount Mfb into the reaction force command value Tr*. The reaction force command value Tr* is a command value of the reaction force torque applied to the steering wheel 12. The reaction force command value Tr* is converted into the angle of the transmission shaft 14.

[0086] The steering operation signal generation process M40a is a process for operating the inverter 72 by inputting a reaction force command value Tr*. In detail, the steering operation signal generation process M40a includes a process for calculating the control operation amount using the torque of the reaction force motor 70 as the control amount and using the reaction force command value Tr* as the target value of the control amount converted into the torque of the reaction force motor 70. The calculation of the operation amount refers to the rotation angle θs and the currents ius, ivs, and iws. In addition, the steering operation signal generation process M40a includes a process for operating the inverter 72 according to the operation amount. Figure 5 , the operation signal MSs of the inverter 72 is described. In fact, the operation signal MSs is an individual operation signal for each switching element of the inverter 72.

[0087] The target angle calculation process M50 is a process for calculating the target angle θp*, which is the target value of the rotation angle of the drive shaft 34. The rotation angle of the drive shaft 34 has a one-to-one correspondence with the steering angle. The target angle calculation process M50 may be, for example, a process for calculating the target angle θp* based on the reaction force command value Tr* using a model of the steering device 10. In this model, for example, the reaction force command value Tr* may be regarded as a torque applied to the transmission shaft 14, assuming that the input shaft 14a and the output shaft 14b are mechanically connected.

[0088] The angle control process M52 is a process for calculating an operation amount for controlling the rotation angle of the drive shaft 34 to the target angle θp*. The operation amount is a steering torque command value Tt* which is a command value of the torque for the steering motor 80 .

[0089] The steering operation signal generation process M54 is a process for operating the inverter 82 by inputting the steering torque command value Tt*. The steering operation signal generation process M54 includes a process for calculating the control operation amount using the torque of the steering motor 80 as the control amount and using the steering torque command value Tt* as the target value of the control amount converted into the torque of the steering motor 80. The calculation of the operation amount refers to the rotation angle θt and the currents iut, ivt, and iwt. In addition, the steering operation signal generation process M54 includes a process for operating the inverter 82 according to the operation amount. Figure 5 The operation signal MSt of the inverter 82 is described in FIG. 8 . In fact, the operation signal MSt is an individual operation signal for each switching element of the inverter 82 .

[0090] <Other Implementation Methods>

[0091] In addition, the above-mentioned embodiments can be implemented by being modified as follows. The above-mentioned embodiments and the following modified examples can be implemented in combination with each other within the scope of no technical contradiction.

[0092] "Regarding the target steering torque calculation process M10"

[0093] The target steering torque calculation process M10 does not necessarily calculate the target steering torque Th* based on the axial force Fa. For example, the target steering torque calculation process M10 may be a process that uses the steering torque Th and the assist torque Ta as inputs to calculate the target steering torque Th*.

[0094] It is not essential that the target steering torque calculation process M10 uses the vehicle speed SPD as an input.

[0095] The input to the target steering torque calculation process M10 is not limited to the above. For example, two or more sample values ​​of the steering angle at different sampling times may be input to the target steering torque calculation process M10. In this case, based on the input, it is possible to realize the identification process when the steering wheel 12 is turned and when it is returned. Therefore, for example, when turning the wheel, the absolute value of the target steering torque Th* may be set to a larger value than when returning the wheel.

[0096] "About open loop operation amount calculation processing"

[0097] The open-loop operation amount calculation process M12 is not limited to the process that uses the target steering torque Th* as an input. For example, the open-loop operation amount calculation process M12 may also be a process that uses the axial force Fa as an input. In this case, the transfer function of the open-loop operation amount calculation process M12 only needs to be the product of the transfer function that calculates the target steering torque Th* based on the axial force Fa and the inverse model of the nominal model Pn.

[0098] "About feedback operation amount calculation processing"

[0099] The feedback operation amount Mfb is not necessarily the sum of the output value of the proportional component using the deviation as input and the output value of the differential component using the deviation as input. For example, the feedback operation amount Mfb may be the sum of the output value of the proportional component using the deviation as input, the output value of the differential component using the deviation as input, and the output value of the integral component using the value corresponding to the deviation as input. Moreover, for example, the feedback operation amount Mfb may be the sum of the output value of the proportional component using the deviation as input and the output value of the integral component using the value corresponding to the deviation as input. At this time, the gain of the integral component may also be changed according to the vehicle speed SPD.

[0100] In addition, the differential means is not limited to the case where the input is the deviation. For example, the differential means may use the steering torque Th as an input. In other words, the differential means may constitute a leading differential type controller.

[0101] The process of making at least one of the gains of the components constituting the feedback operation amount calculation process variable according to the vehicle speed SPD is not essential.

[0102] "About the operation amount calculation process"

[0103] For example, the operation amount calculation process may be composed of only the open-loop operation amount calculation process without the feedback operation amount calculation process. Also, for example, the operation amount calculation process may be composed of only the feedback operation amount calculation process without the open-loop operation amount calculation process.

[0104] "About the Nominal Model Pn"

[0105] The nominal model Pn is not limited to the model exemplified in the above embodiment. For example, a model represented by the following equation (c6) may be used instead of the nominal model Pn used in the steering torque estimation process M32a.

[0106] (-Ktb) / {J·s·s+Ktb}…(c6)

[0107] That is, the polynomial in the denominator of the transfer function of the nominal model Pn may include a zero-order term. In other words, the polynomial in the denominator of the transfer function of the nominal model Pn may include a zero-order term of a differential operator.

[0108] Furthermore, the degree of the polynomial of the denominator of the transfer function of the nominal model Pn does not necessarily have to be second order.

[0109] "About Filter Hd"

[0110] The filter Hd is not limited to the case where the polynomial of the denominator of the transfer function is cubic. For example, the polynomial of the denominator of the transfer function of the filter Hd may be quadratic or higher. In addition, for example, when the polynomial of the denominator of the transfer function of the nominal model Pn is 1st degree, the polynomial of the denominator of the transfer function of the filter Hd may be 2nd or higher degree.

[0111] "About Correction Processing"

[0112] The correction processing is not limited to the processing including the steering torque estimation processing M32, the first disturbance calculation processing M34, the second disturbance calculation processing M36 and the torque command value calculation processing M20. For example, first, the steering torque Th can also be used as the input of the combined processing that combines the inverse model of the nominal model Pn and the filter Hd to calculate the estimated motor torque Tae. In this case, the second only needs to perform the difference calculation processing of calculating the difference between the sum of the open-loop operation amount Mff and the feedback operation amount Mfb and the estimated motor torque Tae. Moreover, thirdly, the torque command value calculation processing M20 can also perform the processing of correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb using the output of the difference calculation processing. In this case, the correction processing is composed of the combined processing, the difference calculation processing and the torque command value calculation processing M20. In addition, the output of the above-mentioned difference calculation processing is a quantity corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0113] "About Operation Processing"

[0114] exist Figure 2In the process shown, the operation process is set as a process that uses the torque of the assist motor 30 as the control amount and uses the value obtained by converting the assist torque Ta as the target value of the control amount into the torque of the assist motor 30, but it is not limited to this. For example, the operation process may also include a process of calculating the target value of the rotation angle of the assist motor 30 based on the axial force Fa. In this case, the operation process is a process of operating the assist motor 30 based on the operation amount of feedback control using the rotation angle of the assist motor 30 as the control amount. In addition, here, the axial force Fa is the sum of the value obtained by correcting the operation amount determined by the open loop operation amount Mff and the feedback operation amount Mfb by the estimated second disturbance torque and the steering torque Th. Therefore, the operation process becomes a process of operating the inverter 32 based on the value obtained by correcting the operation amount determined by the open loop operation amount Mff and the feedback operation amount Mfb by the estimated second disturbance torque. This is a process of controlling the torque of the assist motor 30 in a manner that generates a torque corresponding to the value obtained by correcting the operation amount determined by the open loop operation amount Mff and the feedback operation amount Mfb by the estimated second disturbance torque.

[0115] In addition, the embodiment to which the feedback control including the angle can be applied is not limited to Figure 2 For example, it can also be applied to Figure 3 as well as Figure 6 The embodiment shown.

[0116] "About Steering Controls"

[0117] exist Figure 5 In the illustrated configuration, the device for operating the reaction force motor 70 and the device for operating the steering motor 80 may be independent.

[0118] The steering control device is not limited to a device that includes the PU 42 and the storage device 44 and executes software processing. For example, a dedicated hardware circuit such as an ASIC that executes at least a part of the processing executed in the above embodiment may be included. That is, the steering control device may include a processing circuit having any of the following structures (a) to (c).

[0119] (a) A processing circuit including a processing device for executing all the above-mentioned processes according to a program and a program storage device such as a storage device for storing the program.

[0120] (b) A processing circuit including a processing device that executes part of the above-mentioned processing according to a program, a program storage device, and a dedicated hardware circuit that executes the remaining processing.

[0121] (c) A processing circuit having dedicated hardware circuits for executing all of the above-mentioned processing.

[0122] Here, there may be multiple software execution devices including a processing device and a program storage device. In addition, there may be multiple dedicated hardware circuits.

[0123] "About Steering Control Method"

[0124] The subject that executes the above-mentioned various controls is not limited to the steering control device installed in the vehicle. For example, the driver's mobile terminal may also execute a part of the processing for controlling the target steering torque Th*, such as the disturbance observer M30.

[0125] About the Input Section

[0126] The input unit for inputting the steering torque is not limited to the steering wheel 12 .

[0127] "About the power transmission cut-off state"

[0128] The structure for realizing the cut-off state of the power transmission between the input part for inputting the steering torque and the steered wheel 20 is not limited to Figure 5 For example, a clutch may be provided between the input shaft 14a and the output shaft 14b.

[0129] "About Steering Control Devices"

[0130] As an actuator for steering the steered wheel 20, for example, a device in which the assist motor 30 or the steering motor 80 is arranged coaxially with the steering shaft 16 may be adopted. Furthermore, for example, a device in which the power of the assist motor 30 or the steering motor 80 is transmitted to the steering shaft 16 via a belt speed reducer using a ball screw mechanism may be adopted.

[0131] The steering device capable of changing the relationship between the steering control angle and the steering angle is not limited to the following. Figure 5 The steering device shown cuts off the transmission of power between the steering wheel 12 and the steering wheels 20. For example, a steering device capable of changing the relationship between the steering angle and the steering angle may be configured by using a variable gear as the gear capable of transmitting power between the steering wheel 12 and the steering wheels 20.

Claims

1. A steering control device, wherein: The system is configured to perform operation amount calculation processing, estimation processing, correction processing, and operation processing. The operation amount calculation process is a process for calculating the operation amount of control using the steering torque as the control amount and using the target steering torque as the target value of the control amount. The steering torque is the torque input by the driver to the steering device. The target steering torque is a target value of the steering torque. The above-mentioned estimation process is a process of estimating the disturbance torque using the nominal model and the filter. The correction process is a process of correcting the operation amount based on the disturbance torque estimated by the estimation process. The operation process is a process of operating the motor of the steering device in such a manner as to generate a torque corresponding to the operation amount corrected by the correction process. The degree of the polynomial of the denominator of the transfer function of the filter is greater than the degree of the polynomial of the denominator of the transfer function of the nominal model.

2. The steering control device according to claim 1, wherein: The degree of the polynomial in the denominator of the transfer function of the above nominal model is 2, The degree of the polynomial of the denominator of the transfer function of the filter is 3 or more.

3. The steering control device according to claim 2, wherein: The degree of the polynomial of the denominator of the transfer function of the above-mentioned filter is cubic.

4. The steering control device according to claim 2, wherein: The polynomial in the denominator of the transfer function of the above nominal model contains a first-order term and a zero-order term.

5. The steering control device according to claim 2, wherein: The polynomial in the denominator of the transfer function of the above nominal model does not contain a first-order term.

6. The steering control device according to claim 1, wherein: The above-mentioned operation amount calculation process includes an open-loop operation amount calculation process. The open-loop operation amount calculation process is a process for calculating the open-loop operation amount by inputting the target steering torque into an inverse model of the nominal model. The open-loop operation amount is an operation amount of an open-loop control in which the steering torque is used as the control amount and the target steering torque is used as a target value of the control amount.

7. The steering control device according to claim 1, wherein: The above-mentioned operation amount calculation process includes feedback operation amount calculation process. The feedback operation amount calculation process is a process for calculating the feedback operation amount. The feedback operation amount is an operation amount of feedback control using the steering torque as the control amount and using the target steering torque as a target value of the control amount.

8. The steering control device according to claim 1, wherein: The motor is a motor for steering the steering wheels of the vehicle.

9. The steering control device according to claim 1, wherein: The motor is a motor that applies torque to the input unit in a state where power transmission between the steering wheels of the vehicle and the input unit for the steering torque is cut off.

10. A steering control method, comprising the steps of executing operation amount calculation processing, estimation processing, correction processing and operation processing, The operation amount calculation process is a process for calculating the operation amount of control using the steering torque as the control amount and using the target steering torque as the target value of the control amount. The steering torque is the torque input by the driver to the steering device. The target steering torque is a target value of the steering torque. The above-mentioned estimation process is a process of estimating the disturbance torque using the nominal model and the filter. The correction process is a process of correcting the operation amount based on the disturbance torque estimated by the estimation process. The operation process is a process of operating the motor of the steering device in such a manner as to generate a torque corresponding to the operation amount corrected by the correction process. The degree of the polynomial of the denominator of the transfer function of the filter is greater than the degree of the polynomial of the denominator of the transfer function of the nominal model.

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